The present invention relates to an arrangement for feeding and tightening one or more threads which are formed into stitches or loops in a textile machine. In particular, the arrangement includes a drive mechanism for rotatably driving a thread roller or cylinder in the machine which roller frictionally contacts the thread.
In conventional textile machines, continuously moving thread guides are provided for removing a length of thread from a supply spool at a time prior to forming the thread into a stitch or a loop. After the stitch or loop is formed, the thread guides operate to pull back on the thread, thereby tightening the stitch or loop. Such movement of the thread requires a number of reciprocating machine parts as well as so-called thread brakes, otherwise the thread would be needlessly pulled from the spool upon each movement of the thread guides. In view of the conventional thread feeding operation, up to now, the construction of textile machines has been very complicated and costly and, in addition, these machines have required a great deal of maintenance.
A thread control arrangement is known for use in shuttle embroidery machines wherein an ornamental cord is fed in a manner such that it does not loosen or sag. Ornamental cord can pucker and form small knots to a much greater extent than ordinary embroidery thread. Therefore, it is important that this cord not loosen or sag, i.e., the cord must always be subjected to a uniform and gentle stress.
It is clear, however, that in the case of embroidery threads which are used to produce an embroidered pattern wherein the threads are pulled by a needle, there are certain periods during formation of a stitch in which the thread should not be stressed. In fact, a stitch formation could not be properly carried out in an embroidery machine if the thread is stressed during the first reverse short stroke movement of the needle, since no loop would be formed through which the machine shuttle could pass. Therefore, while the known arrangement may be practically applied when using ornamental cord, it cannot be successfully implemented in the feeding and tightening of embroidery threads. Additionally, in the known arrangement, uniform reciprocating movement of a roller which carries the ornamental cord is provided for all stitches. However, the actual feeding movement of an embroidery thread depends only on the movement of the embroidery foundation, so that a tightening stress such as applied to the ornamental cord would be borne by the embroidery foundation if the known arrangement were used in an embroidery machine.
It will be understood that the length of thread required to allow for advancing movement of the embroidery frame in the machine must be made available by momentarily releasing the thread roller from frictional contact with the thread. It is therefore not possible to implement the above known control arrangement with embroidery thread, since the embroidery operation requires that the thread be released from stress at certain times during the formation of a stitch or loop.
An arrangement for stressing embroidery threads is also known, wherein a thread roller is subjected to a biasing force of a spring after each forward movement of the thread roller, which tends to cause the roller to move in a backward direction as soon as the roller is to be advanced by a tooth-like pawl. Therefore it is only possible with this arrangement to achieve a desired thread advancement wherein the thread is tightened from the embroidery foundation by way of the needle and a separate porcupine roller in the machine, since the thread roller freely rotates as the thread is advanced and only thread brakes provided in the machine counteract the thread advancement. Thus, a further disadvantage results in that tightening of the embroidery thread occurs under stress developed by a spring force, so that thread breakage and, possibly, needle breakage will occur quite often. Also, in this arrangement, only a relatively large mechanical feed movement of the thread roller can be provided because a cam plate which is mounted on a cam shaft provided for rotating the thread roller can only be moved in accordance with movement of the driving mechanism of the embroidery machine. Since, in embroidery machines, a single embroidering operation takes place for each rotation of the main shaft of the machine, the cam shaft with the cam thereon will turn once during a given embroidering operation. Therefore, even if a suitable gear arrangement were available, only a uniform feed movement would result, and the thread roller would follow the downward motion of a locking pawl, thereby hindering the pawl from engaging other teeth. Further, with this arrangement, the thread roller will always undergo substantially uniform reciprocating movement, wherein a particular amount of forward movement results upon advancing the thread. Such an arrangement is, therefore, practically impossible to implement without the use of conventional thread guides.
A thread feeding device for a multi-needle creel embroidery machine is also known, wherein a length of thread corresponding to that required for a stitch is fed for each stitch to be formed. It is, however, necessary to provide thread guides in this arrangement to allow for an additional length of thread required during formation of each stitch. Otherwise, no stitch could be formed and thereafter tightened. In this device, a relatively complicated arrangement provides for advance movement of a thread roller, which movement is derived from the creel driving shaft. It is also possible to avoid excessive stress on the thread when it is tightened. However, when applied to embroidery machines, no significant improvement results since additional complicated mechanical parts must be installed without allowing other parts to be removed. Further, a calculation of the overall length required to be fed for each stitch can not be performed, because a mechanical adjustment takes place in accordance with the creel movement so that the embroidery foundation and the threads themselves can be relieved of stress only to a relatively small degree. In any case, reverse rotation of a separate porcupine roller is not possible with this device, so that thread guides are still required to carry out stitch formation.
An object of the present invention is to provide a textile machine feed arrangement which overcomes the above disadvantages and which enables the feeding and tightening of threads to be adjusted exactly as required, and with which stitches or loops can be tightened by a desired amount.
In accordance with the present invention, a feed arrangement for feeding and tightening a thread in a textile machine of the type which includes a thread roller about which the thread is looped at least once to frictionally contact the thread roller, includes a drive mechanism for rotating the thread roller about its axis in either direction to tighten the thread a desired amount after the thread is formed into a stitch or a loop by the textile machine. The feed arrangement also includes a control device for controlling the drive mechanism in corresponding relationship with the formation of the stitch or loop.
Accordingly, with the arrangement of the present invention, all forward and reverse movements of an embroidery thread relative to the embroidery foundation can be controlled by a thread roller or cylinder. Thus, no stress is applied to the embroidery foundation as a result of tightening of the thread and, further, a number of complex machine parts may be omitted such as, for example, both large and small arm thread guides and their corresponding drive mechanisms. By use of, for example, a punched card control system, a suitable thread feed can be provided wherein an additional thread feed for stitching movement of the needle takes place immediately prior to needle puncture. After each stitch is formed, a suitable amount of thread tightening can be provided. It will be appreciated that proper thread tightening after the formation of each stitch is an essential requirement for high quality embroidered items and, of course, for all high quality textile products.
The thread roller or cylinder in the arrangement of the present invention also operates as a thread brake, so that advancing and reversing movements of the thread during tightening of the stitches or loops can occur without slippage. When using conventional reciprocating thread guides, however, tension is transferred to the thread supply spool and also to the textile products by way of the needle. Thus, the arrangement of the present invention is especially advantageous for use in the manufacture of delicate textile products or in the fabrication of very fine patterns.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which there are illustrated and described preferred embodiments of the invention .